1. Field of the Invention
The present invention relates broadly to the field of solar energy utilization and, more particularly, to a mild steel-stainless steel solar absorber panel and method of fabicating which minimizes the amount of stainless steel required yet accomplishes all the advantages of corrosion resistance in the fluid flow heat transfer system.
2. Description of the Prior Art
The rapid depletion of conventional sources of energy has resulted in an ever widening research for alternatives to such conventional sources as petroleum and natural gas to meet the increasing demand for energy by our society today. One such viable source which is presently commanding a great deal of attention in research and development and in the deployment of experimental units is that of solar energy. Solar flat plate collectors may be employed, inter alia, as sources of heat for homes and buildings and for maintaining an adequate supply of hot water in such installations. Generally, the prior art contains many examples of different ways to utilize solar energy absorbed by solar flat plate collectors of various types. Normally a solar absorber plate having a black body surface is utilized to absorb heat from solar radiation and a heat transfer system is operated in conjunction with the absorber plate to remove useful heat from the absorber and conduct it to a place where it is utilized or stored. Solar collector panels have been utilized to heat a variety of fluid media through heat transfer systems utilizing the solar absorber plate. The higher heat transfer coefficient of liquid media together with the higher heat capacity per unit mass exhibited by such materials as opposed to gaseous fluids results in an ability to obtain an efficient use of the solar energy absorbed.
While research in materials of construction and the use of different configurations to achieve more efficient systems is on-going, one of the greatest drawbacks of present-day solar energy systems is the cost. Reduction in the cost of materials and labor in assembling the solar absorber panels including heat transfer media passage systems along with any increase in efficiency is a desired goal.
One of the primary considerations in the construction of solar energy absorber panels is found in the requirement for long life and durability of the panel itself. An important concern in the design of any liquid media heat transfer system, of course, is overcoming the ever-present danger of corrosion in the system. The solar absorber panels must be sufficiently strong and long-lived in the environment of the solar collector which includes long-term exposure to solar radiation, wide variances in ambient temperature and constant exposure to possibly corrosive media. Mild steel is an abundant, relatively inexpensive commodity which is not appreciably affected either by wide swings in ambient temperature or long-term exposure to solar radiation. However, the relatively high rate of oxidation coupled with the permeability of the oxide layer formed makes mild steel extremely susceptible to liquid-induced corrosion. Thus, while in other respects mild steel is a desirable material for the fabrication of solar absorbers, the problem of corrosion of the fluid-heat transfer passages is very great and must be overcome to produce a solar collector having a long, useful life. This must be done without substantially increasing the risk of galvanic corrosion induced by utilizing dissimilar metal materials such as copper cladding or the like.